The present invention relates to parachutes, and more particularly, to a gliding parachute of the flexible airfoil type having an improved construction that results in superior maneuverability and glide ratio.
For many years parachutes have been constructed by sewing a plurality of panels together to define a hemispherical structure when inflated. Some of these dome-like parachutes have incorporated slits, vents or baffles for controlling the flow of air therethrough, both to facilitate deployment and to provide maneuverability. However, these parachutes are adapted primarily for nearly vertical descent, and generally do not permit a load to be guided over substantial horizontal distances to a target landing area.
Recently, gliding parachutes have been developed for sport jumping, fire fighting, and military applications which can be readily manipulated to carry a load over a substantial distance. A typical gliding parachute is preformed and constrained in such a manner that when inflated it will define an airfoil in longitudinal section. When a load is suspended from this type of inflated parachute, the parachute will glide forwardly and its airfoil shape will provide the necessary lift. By controlling the peripheral edges of the gliding parachute, the parachute and the load can be guided in their path of descent to a target many miles away from the drop point.
Much emphasis has been placed on the fabric and rigging configurations of previous gliding parachutes in an effort to approximate, as close as possible, a conventional airfoil shape. It has been assumed that this would result in maximum lift for a given chute area which would in turn provide the maximum glide ratio. The maximum glide ratio (lift/drag) of prior gliding parachutes has been about three to one. This means that for every foot of vertical descent, the parachute travels three feet horizontally.
Whatever the form of the fabric portion and rigging previously employed in a gliding parachute, there has been a tendency for the shape of the inflated wing to depart from the desired conventional airfoil shape. For example, the leading edge of the wing frequently buckles or folds inwardly under the pressure of air exerted on it as the parachute travels forwardly. Furthermore, the lower surface of the wing has not remained flat. Gliding parachutes have been made with multiple cells for channeling the flow of air in a generally horizontal direction through the parachute to sustain the desired airfoil shape. The various fabric and rigging constructions which have heretofore been utilized in gliding parachutes in an attempt to maintain the conventional airfoil shape have added to the weight and complexity of the parachute.
Prior gliding parachutes have had aspect ratios (span/chord) in the range of 1.5:1 to 1.25:1. It has been conventional in multi-cell gliding parachutes for the maximum camber height to chord ratio to be approximately 0.3:1. The length of the suspension lines has been such that the vertical distance between the top of the head of a jumper and the lower surface of the fabric panel directly above the jumper's head has been at least equal to, and in most cases substantially greater than, the span of the wing. Stating it another way, the maximum ratio of the span to the vertical distance between the lower panel surface and the point of connection of the risers to the harness has been about 1:1 with the parachute inflated. Prior art gliding parachutes have had a suspension point located a distance of 10-15% of the chord length aft of the leading edge.
Pilot chutes have been utilized to facilitate deployment of prior gliding parachutes. Typically, the lines from the pilot chute have been directly connected to the upper canopy fabric, necessitating the extensive utilization of reinforcing strips at the point of attachment of the upper canopy. Furthermore, when a pilot chute has been utilized to facilitate deploymnet of the gliding parachute wing, the pilot chute has thereafter trailed behind the inflated wing as it has glided forwardly at an air speed of 25-30 miles per hour. The pilot chute has thus been a source of significant drag, which has substantially reduced the glide ration of the gliding parachute.
U.S. Pat. No. 3,228,635 of Hughes, et al discloses an early gliding parachute in which a single flexible panel has a plurality of suspension lines connected thereto which are proportioned in length to cause the panel when inflated to assume an airfoil configuration.
U.S. Reissue Pat. No. Re. 26,427 to Jalbert discloses a gliding parachute including an upper canopy and a bottom planar skin connected together by a plurality of vertically extending, spaced apart ribs to define longitudinal channels through which air flows to sustain a conventional airfoil shape. The inflated parachute has a downwardly facing intake opening along its leading edge and a restricted outlet opening along its trailing edge. Connected to the bottom skin of the parachute are a plurality of fabric wedges which provide for even distribution of the forces of the suspension lines to the bottom skin to permit it to retain a flat configuration during flight.
U.S. Pat. No. 3,428,277 to Everett discloses a gliding parachute including a plurality of inflatable ram air scoops along the leading edge of the wing which serve to maintain the leading edge extended and prevent buckling or inward folding thereof. This arrangement supposedly permits the parachute to maintain a preferred angle of attack with respect to the direction of travel during descent so that a lift to drag ratio of approximately 3.7 or more can be achieved. A plurality of spaced apart, vertically aligned vanes are provided along the leading edge of the wing to help stabilize the parachute during flight and to aid in maintaining the desired shape and contour of the ram air scoops. This patent further contains a reference to other U.S. Patents disclosing gliding parachutes.
U.S. Pat. No. 3,524,613 of Reuter, et al discloses a multi-cell ram air type gliding parachute in which the suspension lines have a uniform length in order to impart an arcuate contour to the wing when inflated. The arcuate shape is supposedly utilized to prevent buckling of the central portion of the parachute during flight. The vertical dividers between the upper and lower panels of the wing are provided with openings that permit lateral air flow to equalize air pressure within the adjacent channels.
U.S. Pat. No. 3,724,789 of Snyder discloses a gliding parachute of the multi-channel type in which the suspension lines are secured to the airfoil-shaped ribs between the upper and lower panels of the wing with a plurality of reinforcing tapes to distribute the load and maintain the airfoil shape of the inflated parachute.
In an article entitled "Jump With Me! The Parachute That Glides Like a Plane", by Douglas Garr, Popular Science 19, pages 76-77 and 112, there is described a gliding parachute of the multi-channel type in which a special pilot chute and reefing line system is utilized to soften deployment of the main gliding parachute. When the main wing is fully opened, the pilot chute and deployment bag rest on top of the upper canopy.
In an article entitled "A New Kind of Flying Machine", by Wayne Thoms, published in MECHANIX ILLUSTRATED, September, 1978, pages 36-37, there is disclosed a gliding parachute of the multi-channel type whose suspension lines support a man-carrying carriage including an engine powered propeller.
In an article entitled "Paracraft-The Powered Parafoil", by Luther Hux, published in MODEL AVIATION magazine, September, 1980, pages 62-65 and 122, there is disclosed a gliding parachute of the multi-channel type whose suspension lines support a radio-controlled model airplane fuselage having an engine driven propeller. The article indicates that the parachute has a 2:1 aspect ratio.
U.S. Pat. Nos. 2,214,569; 2,282,407; 2,577,047; and 2,610,008 as well as French Pat. No. 824,349 disclose various arrangements for deploying dome-shaped parachutes utilizing a pilot chute. U.S. Pat. Nos. 2,365,184; 2,358,582; and 3,199,814 disclose various seam and suspension line attachment constructions for parachutes. Finally, U.S. Pat. Nos. 1,562,258; 1,872,705; 2,511,263; 2,520,931; 2,527,553; 2,693,924; 2,696,959; 2,721,716; and 3,173,636 and British Pat. No. 1,102,665 disclose further designs for dome-shaped parachutes.